Neuro Flashcards
(104 cards)
Leg dermatomes
L2 - mid thigh L3 - over the top of the knee L4 - medial calf L5 - lat calf S1 - edge of dorsum foot
Then do stocking distribution
vibration sensation
Test on most distal bony prominence and assess when stops, work up if cannot feel
polyneuropathies that are predominantly motor
GBS, lead poisoning, Charcot Marie tooth
causes of sensory-motor peripheral neuropathy
Metabolic causes: • Diabetes (most common) • hypothyroidism • vitamin deficiencies such as B1, B6 and B12 • uremia
Toxic causes: • alcohol (most common) • chemotherapy agents • antibiotics • Lead (predom motor)
Immune-mediated /inflammatory conditions: • acute onset- GBS (predom motor) • chronic inflammatory demyelinating polyneuropathy (CIDP) • Lambert-eaton / Myasthenia Gravis • rheumatoid arthritis • Sjogren's • SLE • sarcoidosis • ANCA positive vasculitis
Paraneoplastic causes,
• Solid organ malignancy such as lung cancer
• or paraproteinemia
Genetic
• Charcot marie tooth (predom motor)
Electrophysiology in peripheral neuropathy
Nerve conduction studies can distinguish between axonal and demyelinating causes
and if length-dependent
axonal vs demyelinating causes of peripheral neuropathy
distinguish with nerve conduction studies
Axon loss
• trauma / toxic / ischemic / metabolic / genetic conditions
Demyelination
• compressive neurop
• hereditary neurop
• acquired immune-mediated e.g. GBS and CIDP
Interpretation of Romberg’s test
If ataxic and Romberg positive- implies ataxia is sensory in nature (i.e. from loss of proprioception)
If ataxic and Romberg’s not positive- implies ataxia is due to cerebellar dysfunction
Next steps of investigation for peripheral neuropathy
- Bedside tests for diabetes: CBG, urine dipsticks
- Diabetic retinopathy w fundoscopy
- Basic blood tests including antibodies
- Nerve conduction studies
Features of charcot marie tooth
Generalised wasting, particularly distal - inverted champagne bottle
Weakness - high stepped gait/ foot drop
Reduced sensation
Is charcot marie tooth demylinating?
There are many types, some demylinating and some axonal
Type 1 is associated with demyelination
Inheritance of charcot marie tooth
Can be auto dom, recessive or X-linked
Most common is Type 1 which is auto dom
Causes of third nerve palsy
Congenital vs Acquired
Acquired
- Vascular ischemia (commonly diabetes, hypertension)
- Vasc abnormality like aneurysm (esp in PKD)
- SOL
- Inflammation / infection
- Demylinating - MS
- Post-op
- Cavernous sinus thrombosis
Ophthalmoplegic migraine
third nerve palsy signs
- Ptosis (paralysis of levator palpebrae superioris muscle)
- “Down and out” occular deviation
- Pupil becomes fixed and dilated/mydriasis (paralysis of sphincter pupillae)
- Diplopia
Drug triggers for Myasthenia Gravis
Aminoglycosides - Gent, Neomycin Beta blockers Cipro D-penicillamine (for Wilson's) Fluoroquinolones - cipro , Levo Quinine Magnesium Statin
Lambert Eaton Vs myasthenia gravis
In LES:
• rare to have opthalmeplegia
• rare to have severe repiratory muscle weakness
- but has autonomic dysfunction: dry mouth /metallic taste, constipation, and erectile dysfunction
- Fatigue IMPROVES with exercise in LE
- LEMS voltage gated calcium channel
- MG AChR
Features of myotonic dystrophy
Most common adult onset muscular dystrophy
Auto Dom, shows anticipation
CTG repeat mutation
Frontal balding Cataracts Bilat ptosis Facial weakness Testicular atrophy Arrythmia Reduced IQ
Differential of bilat ptosis
- MG
- Muscular dystrophies (Myotonic, Occulopharyngeal)
- Chronic progressive external opthalmeplegia
- Congenital
- Bilat Horner’s
- Syringomyelia
Arm dermatomes
C5 - lat upper arm
C6 - lat lower
C6 specifically median nerve - Lat (thumb) edge of hand
C7 - middle finger
C8 specifically ulnar nerve - medial edge (little finger)
C8 - medial lower arm
T1 - medial upper arm
Jaw jerk reflex
Tests CN V - trigeminal
When abnormal, with upper motor neuron lesions, there is a hyperactive or repeating reflex
(past test says you don’t feel anything normally)
CN for facial expression
CN 7 - facial
can test strength too, by attempting to pull apart
cough reflex
starts with stimulation of irritant receptors with afferents in the vagus nerve (CN X)
Specific sign of ALS
first dorsal interosseous muscle wasting ( thenar eminence ) compared to the hypothenar
AKA split hand sign
MND with only lower motor neuron signs
Spinal muscular atrophy (SMA) - autosomal recessive
Kennedy disease - X-linked recessive
Motor neuropathy with conduction block - acquired and treatable
What is the difference between fasciculation and fibrillation?
Both can be picked up on EMGs
Fibrillations are action potentials of individual fibres
Fasciculation is the summation of them all.. and are VISIBLE